The present research project is proposed in order to study the organization and developmental physiology of cat superior colliculus (SC) cells with regard to retinotectal, corticotectal and intertectal systems. Two related lines of research will be pursued. 1. Developmental studies will document the ontogeny of response and receptive field characteristics of SC cells with special attention given to the maturation of corticotectal and retinotectal systems. Electrophysiological recordings from single cells will be made in the SC and neuronal responses to electrical stimulation of optic pathways and neutral stimuli will be made prior to, during and after temporary inactivation of visual cortex. We will attempt to relate the progressive developmental changes in SC cells to the maturation of specific afferent influences. 2. Behavioral-electrophysiological relationships will also be examined in kittens and adults after (a) extensive occipital-temporal lobectomy, and (b) subsequent intertectal section or contralateral SC removal. Behaviorally, (a) results in an animal resembling the colliculectomized preparation by ignoring contralateral visual stimuli. However, after (b), visually-guided behavior is reinstated. The electrophysiological changes which accompany the behavioral changes will be studied in order to learn which SC properties are essential for visually-guided behavior.